This invention relates generally to imaging systems and more particularly to systems and methods for reducing radiation dosage incident on a subject.
A third generation computed tomography (CT) scanner includes an x-ray source and a detector that are rotated together around a patient. An x-ray beam is passed through the patient and intensity of the x-ray beam is measured on the detector. In some CT imaging systems, an x-ray tube is used to create the x-rays. X-rays are produced when electrons are accelerated against a focal spot or an anode by a high voltage difference between the anode and a cathode of the x-ray tube. These x-rays typically diverge conically from the focal spot, and the diverging x-ray beam is typically passed through a pre-patient collimator to define an x-ray beam profile on the detector. Some CT imaging systems include detector cells arranged on an arc of constant radius from the source. If the collimator is linear, or rectangular, an x-ray beam profile on the detector will become curved along a fan of the detector as an aperture of the collimator is opened along a z-axis. The curvature can result in both unused x-ray dose and degradation in a CT image formed from the curved x-ray beam profile.